To be able to masturbate, 'fap', using both your left or right hand.
Person 1: It's so hard to choose whether to fap with my left or my right hand...
Person 2: You can use both???
Person 1: You can't?
Person 2: Dude, you're so lucky you're ambifaptrous.
Marked by the ability to masturbate easily with either hand. Particularly applicable to males.
"I've been trying to jerk off with my left hand recently to change things up, but it just hasn't worked for me. I wish I was ambimasturbous like Dave. That guy's a wank warrior."
The ability to masturbate with either hand. Alternatively, the ability to switch hit in the five knuckle shuffle.
Guy 1: I burned my right hand prettybad yesterday.
Guy 2: That sucks man, guess you won't be spanking it for a while.
Guy 1: Nah dude, I can still do it with my left hand. I'm ambifapstrous.